This is necessary to get rid of sys-fs/udev from your system without settling for keeping its files around just for some packages to work.
It should already support eudev nicely. What are you seeing?
It works alright but you still need virtual/libgudev installed in order to emerge networkmanager, which pulls in sys-fs/udev. The following is what `emerge -av networkmanager` gives me [ebuild N ] sys-fs/udev-216 USE="acl firmware-loader gudev kmod -doc -introspection (-selinux) -static-libs" 0 KiB [ebuild N ] virtual/libgudev-215-r1 USE="-introspection -static-libs -systemd" 0 KiB [ebuild U ~] net-misc/networkmanager-1.0.0 [0.9.10.1_pre20141101] USE="bluetooth* dhclient ncurses nss ppp wifi -connection-sharing -consolekit -dhcpcd -gnutls -introspection -modemmanager* -resolvconf (-selinux) -systemd -teamd {-test} -vala -wext* -zeroconf" 0 KiB [blocks B ] sys-fs/udev ("sys-fs/udev" is blocking sys-fs/eudev-1.10-r2)
...out of curiosity, 'emerge -1pv sys-fs/eudev' ?
[ebuild R ] sys-fs/eudev-1.10-r2 USE="gudev hwdb introspection keymap kmod modutils openrc rule-generator -doc (-selinux) -static-libs {-test}" ABI_X86="(64) (-32) (-x32)" 0 KiB
...OK, a stupid idea: try putting 'sys-fs/eudev -abi_x86_32' in package.use.stable.mask, then try 'emerge -1pv eudev networkmanager'. Cause if 'gudev' is set on eudev, requirements should be met.
No luck [ebuild R ] sys-fs/eudev-1.10-r2 USE="hwdb keymap kmod modutils openrc rule-generator -doc -gudev -introspection (-selinux) -static-libs {-test}" 0 KiB [ebuild N ] sys-fs/udev-216 USE="acl firmware-loader gudev kmod -doc -introspection (-selinux) -static-libs" 0 KiB [ebuild N ] virtual/libgudev-215-r1 USE="-introspection -static-libs -systemd" 0 KiB [ebuild U ~] net-misc/networkmanager-1.0.0 [0.9.10.1_pre20141101] USE="bluetooth* dhclient ncurses nss ppp wifi -connection-sharing -consolekit -dhcpcd -gnutls -introspection -modemmanager* -resolvconf (-selinux) -systemd -teamd {-test} -vala -wext* -zeroconf" 0 KiB [blocks B ] sys-fs/udev ("sys-fs/udev" is blocking sys-fs/eudev-1.10-r2) Total: 4 packages (1 upgrade, 2 new, 1 reinstall), Size of downloads: 0 KiB Conflict: 1 block (1 unsatisfied) * Error: The above package list contains packages which cannot be * installed at the same time on the same system. (sys-fs/eudev-1.10-r2:0/0::gentoo, ebuild scheduled for merge) pulled in by sys-fs/eudev required by @selected eudev (sys-fs/udev-216:0/0::gentoo, ebuild scheduled for merge) pulled in by >=sys-fs/udev-208-r1:0/0[abi_x86_32(-)?,abi_x86_64(-)?,abi_x86_x32(-)?,abi_mips_n32(-)?,abi_mips_n64(-)?,abi_mips_o32(-)?,abi_ppc_32(-)?,abi_ppc_64(-)?,abi_s390_32(-)?,abi_s390_64(-)?,gudev,introspection?,static-libs?] (>=sys-fs/udev-208-r1:0/0[abi_x86_64(-),gudev]) required by (virtual/libgudev-215-r1:0/0::gentoo, ebuild scheduled for merge) >=sys-fs/udev-208-r1:0/0[abi_x86_32(-)?,abi_x86_64(-)?,abi_x86_x32(-)?,abi_mips_n32(-)?,abi_mips_n64(-)?,abi_mips_o32(-)?,abi_ppc_32(-)?,abi_ppc_64(-)?,abi_s390_32(-)?,abi_s390_64(-)?,static-libs?] (>=sys-fs/udev-208-r1:0/0[abi_x86_64(-)]) required by (virtual/libudev-215-r1:0/1::gentoo, installed) >=sys-fs/udev-208-r1 required by (virtual/udev-215:0/0::gentoo, installed)
This isn't a bug. It's your local configuration problem until proven otherwise.